Reversible air-operated percussive action machine for driving holes in the ground

ABSTRACT

A reversible air-operated percussive action machine for driving holes in the ground has a housing accommodating a hammer 2 capable of reciprocating therein. An air distributor 3 is arranged in the hammer 2 in the form of a fixed tube 12 and a valving member 13 movable relative to the tube. Defined between the tube 12 and valviong member 13 is an accumulating chamber 18 which communicates with an air feeding line 4. An air restrictor is further provided for discharging air from the accumulating chamber 18 when the supply of compressed air to the air feeding line is terminated. The valving member 13 spring-loaded relative to the tube 12 by a spring arranged so that during feeding compressed air to the accumulating chamber 18 the valving member 13 is acted upon by a pressure force directed counter to the action of the spring.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to air-operated percussive action machines usedin civil engineering and mining, and more particularly to machines, fordriving holes in the ground.

2. Description of Related Art

There is known a reversible air-operated percussive action machine fordriving holes in the ground (cf., e.g., USSR Inventor's Certificate No.238,424; IPC E 02 F; F 06 e) comprising a housing, a hammer, an airdistributor and an air feeding hose. The air distributor has the form ofa tube connected to the air feeding hose. The outer surface of the tubeis provided with a threaded portion to connect the tube to the housing.The tube has stop elements for limiting the axial travel thereofrelative to the housing. The frontmost position of the tube ensures theforward percussive action of the machine, whereas the rearmost positionof the tube corresponds to the reverse percussive action. The tube ismoved from one extreme position to the other manually by turning the airfeeding hose.

However, manual rotation of the hose when its length is greater than 40m is a rather labour-consuming procedure. In addition, the abovearrangement fails to assure reliable locking of the tube in the extremepositions, which may result in an unpredicted switchover in thepercussive action mode of operation.

There is also known a reversible air-operated percussive action machinefor driving holes in the ground (cf., USSR Inventor's Certificate No.292,529; IPC E 02 F 5/18) comprising a housing, a hammer, an airdistributor, and an air feeding hose. The air distributor is comprisedof a sleeve fixedly secured relative to the housing, and a spring-loadedtube capable of movements relative to the sleeve.

The tube is provided with shaped lugs received by shaped grooves made inthe sleeve. A switchover of the machine from the forward percussiveaction to the reverse and vice versa is done by terminating the supplyof compressed air and repeated admission thereof to the air feedinghose. In the absence of air pressure the tube is acted upon by thespring to be moved axially and turned inside the sleeve at a certainangle. Readmission of compressed air results in that the tube is lockedin a new position corresponding to a required successive percussiveaction of the machine.

Therefore the switchover in the percussive action mode is done aftereach successive termination of the supply of compressed air andreadmission thereof to the machine. For example, if the machine operatesin the forward percussive action mode, the successive operating modewill be the reverse percussive action of the machine.

One disadvantage of the aforedescribed machine resides in impossibilityof arbitrary variations in the percussive action modes, which leads tocertain inconveniencies in operation. In addition, because the presetpercussive action mode prior to starting the machine by admittingcompressed air thereto, the operator is prone to accidental injury.

There is further known a reversible percussive action machine fordriving holes in the ground (cf., USSR Inventor's Certificate No.652,279; IPC E 02 F 5/18) comprising a housing, an air distributor, andan air feeding hose. The air distributor includes a tube fixedly securedinside the housing, and a spring-loaded valving member built into thetube, the valving member being connected to the air feeding hose. Thevalving member has a lock means enabling to lock the valving member istwo extreme positions providing for two percussive actions of themachine. The valving member is moved from the extreme front positioncorresponding to the forward percussive action of the machine to itsrearmost position ensuring the reverse percussive action manually bypulling at the air feeding hose. The reverse travel of the valvingmember from the rearmost to the frontmost position is done by thespring. The lock means of the valving member is engaged when compressedair is admitted, and disengaged when the supply of compressed air isterminated. Inherent in the aforedescribed machine is a majordisadvantage in that it requires two attendants to control the operationof the machine, one of the attendants looking after the supply ofcompressed air, while the other pulling at the air feeding hose at thehole mouth.

SUMMARY OF THE INVENTION

The invention is therefore directed toward the provision of a reversibleair-operated percussive action machine for driving holes in the groundin which by virtue of preferred interpositioning and a correspondingarrangement of a tube and a valving member it is possible to reverse thepercussive action of the machine by one operator by either initiating orterminating the supply of compressed air to the machine and to assure aswitchover in the percussive action modes at will of the operator.

The essence of the invention resides in that in a reversibleair-operated percussive action machine for driving holes in the groundcomprising a cylindrical housing in which there is disposed forreciprocations a hammer defining inside the housing a forward percussiveaction chamber continuously communicating with an air feeding line and areverse percussive action chamber communicating alternately through ahole provided in the hammer with the forward percussive action chamberand the atmosphere, the hammer having an air distributor in the form ofa guide tube fixedly secured inside the housing and a valving memberspring-loaded relative to the guide tube to be capable of opening andclosing the hole of the hammer and provided with a lock means forlocking the valving member relative to the guide tube in two extremepositions providing for redestribution of air for the machine to operatein the forward and reverse percussive action modes, according to theinvention, the air distributor is provided with an accumulating chamberdefined between the valving member and guide tube and having a means forcommunicating it with the air feeding line, and an air restrictor forletting out air therefrom when the supply of compressed air to the airfeeding line is terminated, the valving member being spring-loadedrelative to the guide tube by a spring means arranged so that whencompressed air is fed to the accumulating chamber a pressure force actson the valving member in a direction counter to the action of the springmeans.

Such an arrangement enables to make the machine easier to operate,because the need for a second attendant otherwise required for pullingthe air feeding hose is obviated.

Preferably, the guide tube and valving member are arranged coaxially toeach other, the accumulating chamber being preferably defined byadjacent stepped portions of the guide tube and valving member.

Such an arrangement ensures small dimensions and simplicity of themachine.

Preferably, the means for communicating the accumulating chamber withthe air feeding line and the means for discharging air therefrom whenthe supply of compressed air to the air feeding line is terminated hasthe form of one air restricting passage communicating the accumulatingchamber with the forward percussive action chamber.

Such an arrangement is less complicated resulting in a greatermanufacturing simplicity.

Advisably, the means for communicating the accumulating chamber with theair feeding line has the form of a hole provided with a non-return valvecommunicating the accumulating chamber with the forward percussiveaction chamber of the machine, whereas the means for discharging airfrom the accumulating chamber when the supply of compressed air isterminated is fashioned as an air restricting passage communicating theaccumulating chamber with the forward percussive action chamber.

This ensures a faster response capability of the machine, because theaccumulating chamber in this case is filled with compressed airinstantaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tovarious preferred embodiments thereof taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of a reversible air-operatedpercussive action machine for driving holes in the ground according tothe invention;

FIG. 2 shows schematically a longitudinal sectional view of an airdistributor when parts of the machine assume a position providing forthe forward percussive action;

FIG. 3 is a schematic longitudinal sectional view of an air distributorwhen the elements of the machine assume a position for the reversepercussive action;

FIG. 4 is a longitudinal sectional view of a modified form of the airdistributor when the parts of the machine provide for the forwardpercussive action; and

FIG. 5 is a schematic longitudinal section of a modified form of the airdistributor when parts of the machine occupy a position for the reversepercussive action.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A reversible air-operated percussive action machine for driving holes inthe ground (FIG. 1) comprises a substantially cylindrical housing 1accommodating a hammer 2 and an air distributor 3 communicable with anair feeding line 4 having the form of a flexible hose. The hammer 2 andthe air distributor 3 divide the interior of the housing 1 into threechambers: a reverse percussive action chamber 5, a forward percussiveaction chamber 6, and a discharge chamber 7. The discharge chamber 7continuously communicates with the atmosphere through holes 8 the totalflow section area of which must provide for reliable exhaust ofcompressed air from the reverse action chamber 5. The direct actionchamber 6 continuously communicates with the air feeding line 4 by wayof a passage 9 (FIG. 2) provided in the air distributor 3. The reverseaction chamber 5 (FIG. 1) communicates through holes 10 and grooves 11made in the hammer 2 with either the direct action chamber 6, or withthe discharge chamber 7, depending on the position assumed by the hammer2 relative to the air distributor 3. The air distributor 3 (FIG. 2) iscomprised of a guide tube 12 a valving member 13 movably arrangedrelative to this tube 12, a spring means in the form of a spring 14, anda lock 15 of the valving member 13 in the form of annular elasticsleeves received by annular recesses 16. The annular recesses 16communicate with the air feeding line 4 by means of holes 17. Themachine is further provided with an accumulating chamber 18 definedbetween the valving member 13 and guide tube 12 adjoining by theirstepped portions (a,b,c,d). This accumulating chamber 18 communicateswith the air feeding line 4 by way of an air restricting passage 19.

The guide tube 12 is an element secured in the housing and having athrough passage continuously communicating the forward percussive actionchamber 6 with the air feeding line 4 and provided with a guide surfaceon which the valving member 13 slides. To ensure a faster response ofthe proposed machine, the accumulating chamber 18 may be additionallycommunicated with the air feeding line through a hole 20 provided with anon-return valve 21, this valve 21 having the form of an elastic sleeve.Hermeticity of the accumulating chamber 18 in points of contact of thestepped portions of the tube 12 with the valving member 13 is ensured byrubber sealing rings 22. In a modification of the air distributorrepresented in FIGS. 2 and 3 the accumulating chamber 18 is defined bydouble-step outer surface of the guide tube 12 and the valving member 13having the form of a stepped sleeve and embracing the tube 12. In amodified form of the air distributor shown in FIGS. 4 and 5 theaccumulating chamber 18 is defined by double-step inner surface of guidetube 12' with steps a' and b' and a valving member 13' mounted thereintoand having the form of a stepped sleeve with steps c' and d'. Thislatter modification provides an annular recess 23 on the guide tube 12'with holes 24 which can be closed by the spring-loaded valving member13'.

In all modifications of the proposed machine the spring means in theform of the spring 14 is arranged so that it acts on the valving member13 and 13' in a direction counter to the direction of the air pressureforce in the accumulating chamber 18 exerted on the valving member.

With reference to FIG. 2, the proposed machine operates in the directpercussive action mode in the following manner. Operation is initiatedby feeding compressed air to the air feeding line 4. The compressed airconveyed through the hole 17 acts to press the lock means 15 to thevalving member 13 and fix it relative to the guide tube 12. At the sametime, the accumulating chamber 18 is charged or filled with compressedair through the passage 19 and hole 20. Compressed air flows along thepassage 9 to the forward percussive action chamber 6, and through theholes 10 (FIG. 2) and grooves 11 (FIG. 1) to the reverse or backwardaction chamber 5. The total flow section area of the holes 10 (FIG. 2)and the total flow section area of the grooves 11 (FIG. 1) must be suchas to ensure reliable discharge of spent air from the chamber 5 to thedischarge chamber 7. Because the working area of the hammer 2 on theside of the reverse action chamber 5 is greater than on the side of theforward action chamber 6, compressed air will act on the hammer 2 tomove it toward the air distributor 3. After the holes 10 (FIG. 2) areblocked by a front distribution edge 25 of the valving member 13, thesupply of compressed air to the reverse percussive action chamber 5(FIG. 1) will be terminated, and a further travel of the hammer 2 willoccur due to expansion of air in the reverse action chamber 5.Compressed air will escape from the reverse action chamber 5 after thehammer 2 moves relative to the air distributor 3 to such an extent thatthe holes 10 (FIG. 2) are opened by a rear distribution edge 26 of thevalving member 13. Subsequent to the discharge of compressed air, thehammer 2 acted upon by the pressure in the forward action chamber 6 willgradually stop to begin its travel in a reverse direction. Upon thehammer 2 being close to assuming its frontmost position, the holes 10are opened by the front air distribution edge 25 of the valving member13 for the return action chamber 5 (FIG. 1) to communicate with theforward action chamber 6. While moving responsive to the forces ofinertia, the hammer 2 delivers an impact on the front portion of thehousing 1. Upon collision with the housing 1 the hammer 2 stops and dueto the pressure in the reverse action chamber 5 starts its travel towardthe air distributor 3. Thereafter, the heretofore described cycle isrepeated. Under the action of impacts the housing 1 is driven into theground, whereby a hole is formed due to soil compaction. The reaction ofthe forces of pressure of compressed air applied to the housing 1 isbalanced by the force of friction between the housing 1 and the soil.

Reverse percussive action is initiated in the following manner. Thesupply of compressed air to the machine is terminated, such as byclosing a valve provided in the air feeding line 4 (FIG. 3). Pressure inthe interior of the air distributor 3 drops suddenly, and the lock means15 no longer holds the valving member 13. Under the action of pressureinside the accumulating chamber 18 the valving member 13 acts tocompress the spring 14 until its coils are in close contact to assume anew position providing for the reverse percussive action of the machine.Before the accumulating chamber 18 is discharged, compressed airreapplied for the valving member 13 to assume a new position relative tothe guide tube 12. The valving member is locked in position due to thatthe lock 15 are pressed to the valving member 13 under the action ofcompressed air entering through the holes 17.

The proposed machine operates in the reverse percussive action mode inthe following manner. Compressed air flows along the passage 9 to theforward action chamber 6 and to the reverse action chamber 5 (FIG. 1)through the holes 10 (FIG. 3) and grooves 11 (FIG. 1). Because theworking area of the hammer 2 on the side of the reverse action chamber 5is greater than on the side of the forward action chamber 6, compressedair will move the hammer 2 toward the air distributor 3. Subsequent toclosing of the holes 10 (FIG. 3) by the front distribution edge 25 ofthe valving member 13 the supply of compressed air to the chamber 5(FIG. 1) will be terminated and a further travel of the hammer 2 will beassured by the expansion of air in the reverse action chamber 5.Compressed air will be discharged from the reverse action chamber 5 whenthe hammer 2 is moved relative to the air distributor 3 to such anextent that the holes 10 (FIG. 3) are opened by the rear distributionedge 26 of the valving member 13. Subsequent to the discharge the hammer2 moves by inertia to deliver an impact on an end nut 28 rigidly securedto the housing 1. The collision makes the hammer 2 stop to reverse itstravel under the action of pressure in the forward action chamber 6. Assoon as the holes 10 are opened by the front distribution edge 25 of thevalving member 13, the compressed air will occupy the reverse actionchamber 5 (FIG. 1). The pressure of air in the chamber 5 will cause thehammer 2 to stop and begin its travel toward the air distributor 3.Thereafter the aforedescribed working cycle is repeated. The impactsdelivered on the end nut 28 will force the machine to move back towardthe hole mouth.

A switchover to the forward percussive action is to be done as follows.The supply of compressed air to the machine is terminated whereafter thepressure in the interior of the air distributor drops sharply and thelock means 15 (FIG. 3) releases the valving member 13. Under the actionof pressure in the accumulating chamber 18 the valving member 13 remainsin a position providing for the reverse percussive action until theaccumulating chamber 18 is discharged, that is until the pressure in theaccumulating chamber 18 drops after the air escapes through the airrestricting passage 19. Subsequent to discharging the accumulatingchamber 18 (discharge time is known from the specifications), the spring14 will cause the valving member 13 to move in a position shown in FIG.2. This is followed by repeated feeding of compressed air and thevalving member 13 is locked relative to the guide tube 12 is a positionproviding for the forward percussive action of the machine. Therefore,for switching over to the forward percussive action it is necessary thatcompressed air be reapplied after the accumulating chamber 18 isdischarged.

While starting the machine after extended idling, the operator is alwaysaware that it will operate in the forward percussive action mode.

For driving holes of small diameter (less than 100 mm across) it is morepreferable to make use of the modification represented in FIGS. 4 and 5.

Construction of this modification is similar to the one represented inFIGS. 1 to 3, the distinction being that the accumulating chamber 18 isdefined by double-step inner surface of the guide tube 12 with steps a',b', and the valving member 13 with steps c', d' mounted thereinto.

This modified form of the reversible air-operated percussive actionmachine functions in the forward action mode when the valving member isin a position best seen in FIG. 4, operation of the machine beingotherwise similar to what has been described with reference to othermodifications.

A switchover to the reverse percussive action is to be done in thefollowing manner. Compressed air supply to the machine is terminated,whereby pressure in the interior of the air distributor 3 (FIG. 5) dropssharply, and the lock means 15 releases the valving member 13'. Thepressure in the accumulating chamber 18 acts to cause the valving member13' to compress the spring 14 until its coils are in close contact, andthe valving member 13' assumes a new position relative to the guide tube12' providing for the reverse percussive action of the machine.Compressed air is reapplied not later than the accumulating chamber 18is discharged through the air restricting passage 19', whereafter thevalving member 19' is locked in a new position (FIG. 5) at which theholes 24 are open.

This modification of the reversible air-operated percussive actionmachine operates in the reverse percussive action mode in the followingmanner. Compressed air is delivered along the passage 9 to the forwardpercussive action chamber 6 and to the reverse action chamber 5 (FIG. 1)through the holes 10 (FIG. 5) and grooves 11 (FIG. 1). Because theworking area of the hammer 2 on the side of the reverse action chamber 5is greater than on the side of the forward action chamber 6, compressedair will act to move the hammer toward the air distributor 3. During afurther travel of the hammer 2 compressed air flows to the reverseaction chamber 5 through the hole 24 (FIG. 5) and annular groove 23 madein the guide tube 12'. Termination of the supply of compressed air tothe chamber 5 (FIG. 1) occurs when the holes 10 (FIG. 5) are blocked bythe distribution edge 27 of the guide tube 12'. A still further travelof the hammer 2 is ensured due to expansion of air in the chamber 5(FIG. 1). Compressed air is caused to escape from the reverse actionchamber 5 when the hammer 2 is displaced relative to the guide tube 12'to such an extent that the holes 10 (FIG. 5) are opened by the reardistribution edge 26' of the guide tube 12'. Subsequent to the dischargeof compressed air, the hammer 2 moves by inertia to deliver an impact onthe end nut 28 rigidly connected to the housing 1. The collision makesthe hammer 2 stop and under the action of pressure in the forward actionchamber 6 to begin travel in the opposite direction. As soon as theholes 10 are opened by the distributing edge 27 of the guide tube 12'compressed air is admitted to the reverse action chamber 5 (FIG. 1). Thepressure of the compressed air in the chamber 5 acts to stop the hammer2 and it starts travelling toward the air distributor 3. Thereafter theheretofore described cycle is repeated. Impacts delivered on the end nut28 (FIG. 5) cause the machine to move in the hole in the oppositedirection.

Most advantageously the present invention can find application fortrenchless laying of underground communications, such as pipelines ofsmall diameter, cables, etc. The proposed machine is very efficient,simple, handy and reliable. It is especially convenient for drivinghorizontal, inclined and vertical holes. Thanks to small overall size,the machine can be used in clustered areas. As compared with similarprior art machines, the proposed machine enables to reduce the amount oflabour consumed during operation and offers higher safety.

We claim:
 1. A reversible air-operated percussive action machine for driving holes in the ground comprising a cylindrical housing (1) in which there is disposed for reciprocations a hammer (2) defining inside the housing (1) a forward percussive action chamber (6) continuously communicating with an air feeding line (4) and a reverse percussive action chamber (5) communicating alternately through a hole (10) provided in the hammer (2) with the forward percussive action chamber (6) and the atmosphere, the hammer (2) having an air distributor (3) in the form of a guide tube (12) fixedly arranged inside the housing (1) and a valving member (13) spring-loaded relative to the guide tube and capable of opening and closing the hole (10) of the hammer (2) and provided with a lock means (15) for locking the valving member (13) relative to the guide tube (12) in two extreme positions providing for redistribution of air for the machine to operate in the forward and reverse percussive action modes, characterized in that the air distributor (3) comprises means for defining an accumulating chamber (18) between the valving member (13) and guide tube (12), means for communicating the accumulating chamber with the air feeding line (4), and an air restrictor for letting out air from the accumulating chamber when the supply of compressed air to the air feeding line (4) is terminated, the valving member being spring-loaded relative to the guide tube (12) by a spring means arranged so that when compressed air is fed to the accumulating chamber (18) a pressure force acts on the valving member (13) in a direction counter to the action of the spring means, said air restrictor placing said accumulating chamber (18) in constant communication with said air feeding line (4).
 2. A machine according to claim 1, characterized in that the guide tube (12) and valving member (13) are arranged coaxially to each other, whereas the accumulating chamber (18) is defined by adjacent stepped portions (a,b) of the guide tube (12) and stepped portions (c,d) of the valving member (13).
 3. A reversible air-operated percussive action machine for driving holes in the ground comprising a cylindrical housing (1) in which there is disposed for reciprocations a hammer (2) defining inside the housing (1) a forward percussive action chamber (6) continuously communicating with an air feeding line (4) and a reverse percussive action chamber (5) communicating alternately through a hole (10) provided in the hammer (2) with the forward percussive action chamber (6) and the atmosphere, the hammer (2) having an air distributor (3) in the form of a guide tube (12) fixedly arranged inside the housing (1) and a valving member (13) spring-loaded relative to the guide tube and capable of opening and closing the hole (10) of the hammer (2) and provided with a lock means (15) for locking the valving member (13) relative to the guide tube (12) in two extreme positions providing for redistribution of air for the machine to operate in the forward and reverse percussive action modes, characterized in that the air distributor (3) comprises means for defining an accumulating chamber (18) between the valving member (13) and guide tube (12), means for communicating the accumulating chamber with the air feeding line (4), and an air restrictor for letting out air from the accumulating chamber when the supply of compressed air to the air feeding line (4) is terminated, the valving member being spring-loaded relative to the guide tube (12) by a spring means arranged so that when compressed air is fed to the accumulating chamber (18) a pressure force acts on the valving member (13) in a direction counter to the action of the spring means, and said means for communicating the accumulating chamber with the air feeding line (4) having the form of a hole (20) provided with a non-return valve (21) communicating the accumulating chamber (18) with the forward percussive action chamber (6), whereas said air restrictor for discharging air from the accumulating chamber (18) when the supply of air to the air feeding line (4) is terminated is fashioned as an air restricting passage (19) communicating the accumulating chamber (18) with the forward percussive action chamber (6).
 4. A reversible air-operated percussive action machine for driving holes in the ground comprising a cylindrical housing (1) in which there is disposed for reciprocations a hammer (2) defining inside the housing (1) a forward percussive action chamber (6) continuously communicating with an air feeding line (4) and a reverse percussive action chamber (5) communicating alternately through a hole (10) provided in the hammer (2) with the forward percussive action chamber (6) and the atmosphere, the hammer (2) having an air distributor (3) in the form of a guide tube (12) fixedly arranged inside the housing (1) and a valving member (13) spring-loaded relative to the guide tube and capable of opening and closing the hole (10) of the hammer (2) and provided with a lock means (15) for locking the valving member (13) relative to the guide tube (12) in two extreme positions providing for redistribution of air for the machine to operate in the forward and reverse percussive action modes, characterized in that the air distributor (3) comprises means for defining an accumulating chamber (18) between the valving member (13) and guide tube (12), means for communicating the accumulating chamber with the air feeding line (4), and an air restrictor for letting out air from the accumulating chamber when the supply of compressed air to the air feeding line (4) is terminated, the valving member being spring-loaded relative to the guide tube (12) by a spring means arranged so that when compressed air is fed to the accumulating chamber (18) a pressure force acts on the valving member (13) in a direction counter to the action of the spring means, said guide tube (12) and valving member (13) being arranged coaxially to each other, whereas the accumulating chamber (18) is defined by adjacent stepped portions (a,b) of the guide tube (12) and stepped portions (c,d) of the valving member (13) and said means for communicating the accumulating chamber with the air feeding line (4) having the form of a hole (20) provided with a non-return valve (21) communicating the accumulating chamber (18) with the forward percussive action chamber (6), whereas said air restrictor for discharging air from the accumulating chamber (18) when the supply of air to the air feeding line (4) is terminated is fashioned as an air restricting passage (19) communicating the accumulating chamber (18) with the forward percussive action chamber (6). 